One mole of an ideal monatomic gas is at $300\ \text{K}$ and $1.0 \times 10^{5}\ \text{Pa}$ in a thermally insulated cylinder. The pressure outside the piston is suddenly raised to $2.0 \times 10^{5}\ \text{Pa}$ and then kept steady, so the gas is squeezed quickly until it is again at rest, at $2.0 \times 10^{5}\ \text{Pa}$. Ignore friction and the mass of the piston, and take $R = 8.314\ \text{J/(mol K)}$. Which of the following statements are correct?